1. Field
The present invention relates to a sensor for measuring a current flowing in an electrical conductor, and more particularly to a sensor with two or more modes for measuring current.
2. Discussion of Related Art
The rising number of electrical consumer loads in motor vehicles has created an ever-increasing demand for power in on-board electrical systems of vehicles. As a result, the load on the on-board battery, which serves as a backup during operation of the vehicle and maintains the vehicle's voltage supply when the engine is switched off, is becoming ever greater. These greater loads can lead to a failure to completely charge the battery during engine operation, particularly where the vehicle is subject to increased use for short-run operations. Such incompletely charged batteries can result in dead batteries, vehicle break downs, and/or an inability to start a vehicle due to a low battery voltage.
Energy management systems are increasingly being used in vehicles to prevent battery charging failures. Such energy management systems are intended to ensure that the charging condition of the battery does not reach a critical state and to ensure a positive charging balance of the battery. These systems perform analysis of the battery's condition, based on measured variables for battery current, battery voltage and battery temperature. In many systems, the detection of a charging or discharging current is significant in keeping the battery at a non-critical charge level to ensure the ability to start a vehicle.
The sensor shown in FIGS. 3 and 4 is known from the prior art for use in a motor vehicle for monitoring flowing currents. As shown, a measuring shunt 202 is inserted in earth conductor 201 to detect the battery current. An analyzing unit 203 directly measures the voltage drop at the measuring shunt and from this measurement calculates the level of current that is flowing. The measuring shunt may be made of Manganin.
FIG. 3 shows the measuring set-up associated with a sensor like that shown in FIG. 4. A car battery 205 is connected to the vehicle earth by way of an earth conductor 201. The sensor, comprising measuring shunt 202 and analyzing unit 203, is integrated into earth conductor 201. Electrical consumer loads 206 of the vehicle are connected to the positive pole of battery 205 by way of a conductor 207.
The sensor and configuration of FIGS. 3 and 4 do exhibit some disadvantages. The measuring shunt has to be integrated into the conductor that carries the current, which causes additional design expenditure since it is necessary to ensure that shear and tensile forces are not imparted to the measuring shunt. Deformation of the measuring shunt may influence the measured result and, in some cases, can lead to a fault in the sensor. Moreover, the configuration of FIGS. 3 and 4 necessarily incurs a heat loss via the measuring shunt. By way of example, even when using low resistances, such as those associated with a 100 mW measuring shunt, heat is still lost and has to be dissipated.
To overcome disadvantages in prior art designs, there is a need for a sensor that can detect the charging and/or discharging current over a very wide range, for example from −200 A to 1500 A. There is also a need for a suitable sensor, such as for use in energy management of a vehicle, that can cover this wide range of currents and have a high dynamic response.